Inverting homotopy groups of spectra












7














Let $X$ be a spectrum. Is there a canonical construction/functor that would associate to this spectrum, an inverse spectrum $X'$, in the sense that $$pi_*(X)cong pi_{-*}(X')?$$



To be more precise, such a spectrum $X'$ can always be constructed by attaching cells to produce the right homotopy groups, but is there a more conceptual way of creating it?










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    7














    Let $X$ be a spectrum. Is there a canonical construction/functor that would associate to this spectrum, an inverse spectrum $X'$, in the sense that $$pi_*(X)cong pi_{-*}(X')?$$



    To be more precise, such a spectrum $X'$ can always be constructed by attaching cells to produce the right homotopy groups, but is there a more conceptual way of creating it?










    share|cite|improve this question



























      7












      7








      7


      2





      Let $X$ be a spectrum. Is there a canonical construction/functor that would associate to this spectrum, an inverse spectrum $X'$, in the sense that $$pi_*(X)cong pi_{-*}(X')?$$



      To be more precise, such a spectrum $X'$ can always be constructed by attaching cells to produce the right homotopy groups, but is there a more conceptual way of creating it?










      share|cite|improve this question















      Let $X$ be a spectrum. Is there a canonical construction/functor that would associate to this spectrum, an inverse spectrum $X'$, in the sense that $$pi_*(X)cong pi_{-*}(X')?$$



      To be more precise, such a spectrum $X'$ can always be constructed by attaching cells to produce the right homotopy groups, but is there a more conceptual way of creating it?







      at.algebraic-topology stable-homotopy






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      edited Dec 22 at 18:24









      David White

      11.5k460100




      11.5k460100










      asked Dec 22 at 16:56









      user09127

      1305




      1305






















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          14














          Not exactly what you asked for, but there is the Brown-Comenetz dual of $X$, $I_{mathbb{Q}/mathbb{Z}}X$, which has the property that its homotopy groups are Pontryagin dual to the homotopy groups of $X$ (in the negative degree):



          $pi_{-ast}(I_{mathbb{Q}/mathbb{Z}}X) simeq Hom(pi_ast(X),mathbb{Q}/mathbb{Z})$



          So, if the homotopy groups of $X$ are all finite, then the Pontragin dual groups will be (non-canonically) isomorphic and this will have the required property.



          See here for more details






          share|cite|improve this answer























          • There's a question that always bothered me. Maybe you know the answer. How canonical is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$? More precisely, is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$ a functor from the $infty$-groupoid of spectra to itself? It's obviously a functor at the level of the homotopy category. But what about at the $infty$-groupoid level?
            – André Henriques
            2 days ago












          • @AndréHenriques I've probably misunderstood your question, but does this answer it? If $I_mathbf{Q/Z} := I_mathbf{Q/Z}(S^0)$ denotes the Brown-Comenetz dualizing spectrum, then $I_mathbf{Q/Z}(X) = F(X, I_mathbf{Q/Z})$, and this is functorial in $X$.
            – skd
            yesterday












          • @skd. Yes, of course... that does answers my question. But I now realise that I haden't asked the right question. Here's the right question: what is $I_{mathbb Q/mathbb Z}$? More precisely, is there a way to define it up to contractible space of choices?
            – André Henriques
            yesterday











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          1 Answer
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          active

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          14














          Not exactly what you asked for, but there is the Brown-Comenetz dual of $X$, $I_{mathbb{Q}/mathbb{Z}}X$, which has the property that its homotopy groups are Pontryagin dual to the homotopy groups of $X$ (in the negative degree):



          $pi_{-ast}(I_{mathbb{Q}/mathbb{Z}}X) simeq Hom(pi_ast(X),mathbb{Q}/mathbb{Z})$



          So, if the homotopy groups of $X$ are all finite, then the Pontragin dual groups will be (non-canonically) isomorphic and this will have the required property.



          See here for more details






          share|cite|improve this answer























          • There's a question that always bothered me. Maybe you know the answer. How canonical is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$? More precisely, is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$ a functor from the $infty$-groupoid of spectra to itself? It's obviously a functor at the level of the homotopy category. But what about at the $infty$-groupoid level?
            – André Henriques
            2 days ago












          • @AndréHenriques I've probably misunderstood your question, but does this answer it? If $I_mathbf{Q/Z} := I_mathbf{Q/Z}(S^0)$ denotes the Brown-Comenetz dualizing spectrum, then $I_mathbf{Q/Z}(X) = F(X, I_mathbf{Q/Z})$, and this is functorial in $X$.
            – skd
            yesterday












          • @skd. Yes, of course... that does answers my question. But I now realise that I haden't asked the right question. Here's the right question: what is $I_{mathbb Q/mathbb Z}$? More precisely, is there a way to define it up to contractible space of choices?
            – André Henriques
            yesterday
















          14














          Not exactly what you asked for, but there is the Brown-Comenetz dual of $X$, $I_{mathbb{Q}/mathbb{Z}}X$, which has the property that its homotopy groups are Pontryagin dual to the homotopy groups of $X$ (in the negative degree):



          $pi_{-ast}(I_{mathbb{Q}/mathbb{Z}}X) simeq Hom(pi_ast(X),mathbb{Q}/mathbb{Z})$



          So, if the homotopy groups of $X$ are all finite, then the Pontragin dual groups will be (non-canonically) isomorphic and this will have the required property.



          See here for more details






          share|cite|improve this answer























          • There's a question that always bothered me. Maybe you know the answer. How canonical is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$? More precisely, is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$ a functor from the $infty$-groupoid of spectra to itself? It's obviously a functor at the level of the homotopy category. But what about at the $infty$-groupoid level?
            – André Henriques
            2 days ago












          • @AndréHenriques I've probably misunderstood your question, but does this answer it? If $I_mathbf{Q/Z} := I_mathbf{Q/Z}(S^0)$ denotes the Brown-Comenetz dualizing spectrum, then $I_mathbf{Q/Z}(X) = F(X, I_mathbf{Q/Z})$, and this is functorial in $X$.
            – skd
            yesterday












          • @skd. Yes, of course... that does answers my question. But I now realise that I haden't asked the right question. Here's the right question: what is $I_{mathbb Q/mathbb Z}$? More precisely, is there a way to define it up to contractible space of choices?
            – André Henriques
            yesterday














          14












          14








          14






          Not exactly what you asked for, but there is the Brown-Comenetz dual of $X$, $I_{mathbb{Q}/mathbb{Z}}X$, which has the property that its homotopy groups are Pontryagin dual to the homotopy groups of $X$ (in the negative degree):



          $pi_{-ast}(I_{mathbb{Q}/mathbb{Z}}X) simeq Hom(pi_ast(X),mathbb{Q}/mathbb{Z})$



          So, if the homotopy groups of $X$ are all finite, then the Pontragin dual groups will be (non-canonically) isomorphic and this will have the required property.



          See here for more details






          share|cite|improve this answer














          Not exactly what you asked for, but there is the Brown-Comenetz dual of $X$, $I_{mathbb{Q}/mathbb{Z}}X$, which has the property that its homotopy groups are Pontryagin dual to the homotopy groups of $X$ (in the negative degree):



          $pi_{-ast}(I_{mathbb{Q}/mathbb{Z}}X) simeq Hom(pi_ast(X),mathbb{Q}/mathbb{Z})$



          So, if the homotopy groups of $X$ are all finite, then the Pontragin dual groups will be (non-canonically) isomorphic and this will have the required property.



          See here for more details







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited 2 days ago

























          answered Dec 22 at 17:37









          Sam Gunningham

          4,3571929




          4,3571929












          • There's a question that always bothered me. Maybe you know the answer. How canonical is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$? More precisely, is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$ a functor from the $infty$-groupoid of spectra to itself? It's obviously a functor at the level of the homotopy category. But what about at the $infty$-groupoid level?
            – André Henriques
            2 days ago












          • @AndréHenriques I've probably misunderstood your question, but does this answer it? If $I_mathbf{Q/Z} := I_mathbf{Q/Z}(S^0)$ denotes the Brown-Comenetz dualizing spectrum, then $I_mathbf{Q/Z}(X) = F(X, I_mathbf{Q/Z})$, and this is functorial in $X$.
            – skd
            yesterday












          • @skd. Yes, of course... that does answers my question. But I now realise that I haden't asked the right question. Here's the right question: what is $I_{mathbb Q/mathbb Z}$? More precisely, is there a way to define it up to contractible space of choices?
            – André Henriques
            yesterday


















          • There's a question that always bothered me. Maybe you know the answer. How canonical is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$? More precisely, is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$ a functor from the $infty$-groupoid of spectra to itself? It's obviously a functor at the level of the homotopy category. But what about at the $infty$-groupoid level?
            – André Henriques
            2 days ago












          • @AndréHenriques I've probably misunderstood your question, but does this answer it? If $I_mathbf{Q/Z} := I_mathbf{Q/Z}(S^0)$ denotes the Brown-Comenetz dualizing spectrum, then $I_mathbf{Q/Z}(X) = F(X, I_mathbf{Q/Z})$, and this is functorial in $X$.
            – skd
            yesterday












          • @skd. Yes, of course... that does answers my question. But I now realise that I haden't asked the right question. Here's the right question: what is $I_{mathbb Q/mathbb Z}$? More precisely, is there a way to define it up to contractible space of choices?
            – André Henriques
            yesterday
















          There's a question that always bothered me. Maybe you know the answer. How canonical is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$? More precisely, is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$ a functor from the $infty$-groupoid of spectra to itself? It's obviously a functor at the level of the homotopy category. But what about at the $infty$-groupoid level?
          – André Henriques
          2 days ago






          There's a question that always bothered me. Maybe you know the answer. How canonical is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$? More precisely, is the assignment $Xmapsto I_{mathbb Q/mathbb Z}X$ a functor from the $infty$-groupoid of spectra to itself? It's obviously a functor at the level of the homotopy category. But what about at the $infty$-groupoid level?
          – André Henriques
          2 days ago














          @AndréHenriques I've probably misunderstood your question, but does this answer it? If $I_mathbf{Q/Z} := I_mathbf{Q/Z}(S^0)$ denotes the Brown-Comenetz dualizing spectrum, then $I_mathbf{Q/Z}(X) = F(X, I_mathbf{Q/Z})$, and this is functorial in $X$.
          – skd
          yesterday






          @AndréHenriques I've probably misunderstood your question, but does this answer it? If $I_mathbf{Q/Z} := I_mathbf{Q/Z}(S^0)$ denotes the Brown-Comenetz dualizing spectrum, then $I_mathbf{Q/Z}(X) = F(X, I_mathbf{Q/Z})$, and this is functorial in $X$.
          – skd
          yesterday














          @skd. Yes, of course... that does answers my question. But I now realise that I haden't asked the right question. Here's the right question: what is $I_{mathbb Q/mathbb Z}$? More precisely, is there a way to define it up to contractible space of choices?
          – André Henriques
          yesterday




          @skd. Yes, of course... that does answers my question. But I now realise that I haden't asked the right question. Here's the right question: what is $I_{mathbb Q/mathbb Z}$? More precisely, is there a way to define it up to contractible space of choices?
          – André Henriques
          yesterday


















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